All Figures

	Figure 1: uv-plane coverage obtained on Ori C with the four IOTA array configurations used. The relatively strong asymmetry in the uv-plane coverage mainly results from the position of Ori C relatively close to the celestrial equator.
Open with DEXTER


In the text

	Figure 2: uv-plane coverage obtained on Ori D with two IOTA array configurations. Symbols and colors as in Fig. 1.
Open with DEXTER


In the text

Figure 3: Left, Middle: bispectrum speckle J and V'-band images reconstructed from BTA-data. Right: aperture synthesis image of Ori C reconstructed from our IOTA H-band data. Besides the false-color representation in the upper row, we show the images below as contours with the best-fitted positions marked with star symbols (see Table 3). In the image in the lower right corner, the restoring beam for the IOTA aperture synthesis image is shown as an inset. Over the six year interval covered by the images, orbital motion is clearly conceivable (1999/2004/2005: /24/14 mas; /191/163).

Open with DEXTER


In the text

Figure 4: Visibilities and closure phases derived from the recorded IOTA interferograms for Ori C as a function of hour angle (points with error bars). The solid line shows the binary model fit, described in more detail in Sect. 4. The different symbols represent the different detector modes used (see Table 1). The data for each detector mode was calibrated separately, so the scattering of the data groups represents the typical calibration errors.

Open with DEXTER


In the text

	Figure 5: Projection of the sampled Fourier plane along the fitted binary PA of ( ), clearly revealing the binary signature. The dashed line shows the theoretical cosine visibility profile for a binary star with separation 13.55 mas and intensity ratio 0.28.
Open with DEXTER


In the text

	Figure 6: Visibilities and closure phases derived from the recorded IOTA interferograms for Ori D (points with error bars). The solid line shows the binary model fit, described in more detail in Sect. 4.2.
Open with DEXTER


In the text

Figure 7: Top: two best-fit apparent orbits of the Ori C binary system (solid and dashed line). Each position measurement (see Table 3) is connected to its predicted position with an O-C line. Besides our orbital solutions (see Table 4), the line of nodes and the predicted positions for the interval 2007.0 to 2008.5 (increments of 0.25 yrs) are shown. North is up and east is to the left. Bottom: radial velocity variations of both components computed for our orbital solutions using the method presented by Pourbaix (1998). For the mass ratio , we assume 0.47, as obtained from our modeling of the flux ratio presented in Sect. 5.4. When computing the radial velocity curve, the (unknown) system velocity V0 represents a free-parameter corresponding to a velocity offset, which we set to -5 km s-1 for this plot. The radial velocity measurements (points with errorbars) were taken from Vitrichenko (2002b).

Open with DEXTER


In the text

Figure 8: Measured intensity ratio of the Ori C components as a function of wavelength (points with errorbars). For various spectral-type combinations, the curves show the expected intensity ratio, assuming the stars contribute purely photospheric emission (black-body emission with luminosities and effective temperatures as given in the stellar evolution models from Martins et al. (2005, M05) and Claret (2004, C04)).

Open with DEXTER


In the text

Figure 9: HR-diagram with PMS evolutionary tracks (Z=0.02; thin solid lines with the corresponding masses labeled aside). For masses ( ), the tracks from Siess et al. 2000 (Bernasconi & Maeder 1996) were used. The three dotted lines represent the isochrones for 0.3, 0.6, and 1.0 Myr (Bernasconi & Maeder 1996). Using the synthetic colors and bolometric corrections compiled by Kenyon & Hartmann (1995, including data from Johnson 1966, Bessell & Brett 1988, and others# and the O star colors by Martins et al. (2005) and Martins & Plez (2006), we converted the measured photometry for Ori C1, C2, D1, and D2 into the corresponding allowed locations in the HR-diagram (thin red lines).

Open with DEXTER


In the text